Project Summary/Abstract. Candidate: My goal is to become an independent scientist investigating endolysosomal dysfunction in neurodegenerative disease, with a focus on endosomal maturation and trafficking. My background is in neuropharmacology and mechanisms of rodent behavior, but I have recently shifted to investigating abnormal endosomal trafficking in progranulin-insufficient mice. Having received my PhD in 2012, this is my final cycle of eligibility for a K99/R00 award. My goal is to establish a laboratory to investigate endolysosomal dysfunction in multiple genetic models of frontotemporal dementia (FTD). After establishing expertise in this field, I hope to investigate models of Alzheimer?s disease and eventually begin to explore how environmental factors (ex. exercise, environmental enrichment, etc.) interact with neuronal endolysosomal function to influence behavior. Training: In addition to my primary mentor, Dr. Erik Roberson, I have assembled an advisory committee that includes experts on endolysosomal function (Dr. James Collawn) and exosome analysis (Dr. Andrew West), as well as Dr. David Standaert, the chair of our Department of Neurology with extensive postdoctoral training experience. I will present at international meetings and take courses (both external and internal to UAB) for technical training (cell biology, endosomal trafficking, and exosome analysis), professional development (lab management, budgeting, scientific writing, and the tenure process), and ethical conduct of research. Research: Loss-of-function mutations in progranulin (GRN) are a major cause of FTD, and are thought to cause FTD through progranulin haploinsufficiency. This proposal will test the hypothesis that FTD due to progranulin (GRN) mutations (FTD-GRN) is caused by endolysosomal dysfunction. We hypothesize that progranulin insufficiency impairs lysosomal activity, which disrupts late endosomal trafficking and ultimately causes FTD in humans and disrupts behavior in mice. Progranulin is critical for normal lysosomal function as complete progranulin deficiency causes a lysosomal storage disorder. In preliminary studies, we have observed elevated levels of exosome in plasma from FTD-GRN patients, as well as progranulin-insufficient (Grn+/?) mouse plasma and primary neuron culture media. In aim 1, we will test whether this enhanced exosome production reflects a shift in trafficking of multivesicular bodies (MVBs) away from lysosomal degradation and toward exosome secretion. In aim 2A we will determine if lysosomal dysfunction causes this enhanced exosome secretion and in aim 2B we will determine if this endolysosomal dysfunction causes behavior deficits in Grn+/? mice. In aim 3 we will compare levels of late endosomal/lysosomal proteins and MVB morphology in brains of FTD-GRN patients with healthy controls and Alzheimer?s disease patients to control for nonspecific effects of neurodegeneration. These studies will give me experience with primary neuronal culture, endosomal tracking analysis, shRNA gene knockdown, and exosome isolation and analysis.